There is accumulating evidence that retinal microglia are indeed associated with diabetic retinopathy. Minocycline is a second-generation tetracycline, which has anti-inflammatory properties that are separate from its anti-microbial properties. The study objective is to investigate the safety and efficacy of minocycline, a microglia inhibitor, in the treatment of diabetic macular edema. This is a prospective, non-randomized, uncontrolled, single group, single center pilot study to investigate the safety and efficacy of minocycline as a microglia inhibitor in patients with DME who have already been treated with standard-of-care laser or who are not amenable to standard-of-care therapy.